IE43418B1

IE43418B1 - Blend of thermoplastic polymers including block radial polymers of the butadiene-styrene type

Info

Publication number: IE43418B1
Application number: IE1890/76A
Authority: IE
Original assignee: Abbott Lab
Priority date: 1975-08-26
Filing date: 1976-08-25
Publication date: 1981-02-25
Also published as: IE43418L; IT1065442B; US4048254A; ZA764159B; FR2323737A1; FR2323737B1; AU504069B2; BR7605487A; GB1515240A; NZ181618A; AU1617576A; MX3426E; SE414043B; SE7609333L; DE2637865A1; JPS5226543A; US4117035A; PH14391A; CA1065990A

Abstract

1515240 Radial block butadiene/styrene copolymer compositions ABBOTT LABORATORIES 25 Aug 1976 [26 Aug 1975] 35416/76 Headings C3M and C3R Compositions having high clarity and resealability comprise (1) 10-90% butadiene/ styrene radial block copolymer of 85-60% butadiene and 15-40% styrene, (2) 90-10% butadiene/styrene radial block copolymer having a different butadiene content of 85-60% and a different styrene content of 15-40% and (3) 5-75% based on the block copolymers of clear polymeric material selected from acrylics, thermoplastic epoxies, styrene/acrylonitrile copolymers, polycarbonates, polyolefins, polyesters, polyvinyl chloride, olefin/vinyl chloride copolymers, polyether and polyester urethanes, methacrylate acrylonitrile styrene/butadiene and methacrylate/styrene/butadiene copolymers. Exemplified compositions comprise radial block copolymers and butadiene/styrene/methyl methacrylate copolymer and/or thermoplastic polyether polyurethane, polyester urethane or butadiene/styrene/methyl methaerylate/acrylonitrile. The compositions may be moulded into medical plastic products such as containers, seals, closures, tubing and syringe plunger tips.

Description

This invention relates to thermoplastic polymer compositions which are useful in moulding plastic materials for contact with body fluids. More particularly, it relates to a thermoplastic polymer composed of radical block copolymers of butadiene and styrene type which have blended with them additional polymeric materials to form a plastic composition having a high degree of clarity and which are particularly useful in extruding or molding tubing, drip chambers and other components useful in the field of parenteral administration Recently, radial block copolymers of butadiene and styrene have become of particular interest in that they display high tensile strength without vulcanization or filler reinforcement. These copolymers can be processed on conventional plastics or rubber equipment without the addition of plasticizers. In U.S. Patents Nos. 3,281,383 and 3,078,254, processes for making such radial block copolymers are described. Further, particular blends of vulcanized butadiene-styrene block copolymers are described in U.S. Patent No. 3,646,161, In U.S. Patent No. 3,562,355, a mechanical blend of a butadiene-styrene copolymer with a polyester urethane is described. The prior art nowhere describes a blend of nonvulcanized radial block copolymers of butadiene and styrene wherein the butadiene-styrene copolymer is present in a minimum proportion so that when they are blended with certain - 3 other polymeric materials, they will form a plastic materia] composition having sufficient clarity, hard ness, tensile strength and elongation to be readily adaptable for use in producing plastics material articles for contact with parenteral fluids. In addition, the prior art nowhere describes a plastics material composition which is suitable for use in the medical plastics field and which will have low alkaline extraction values so that components of the composition are not extracted by the fluids to be administered.

The present invention seeks to provide a novel blend of radial block copolymers of butadiene and styrene with certain other polymeric materials, it further seeks to provide a thermoplastic composition of the radial block copolymer type which has a high degree of clarity so that it can replace polyvinylchloride as a material for forming a medical plastic product such as tubing, drip chambers, injection reseal device and other parenteral administration equipment; it also seeks to provide a novel radial block copolymer mixture which can be readily molded, extruded and otherwise processed by conventional processes; a thermoplastic material which is compatible with the conventional plasticizers, fillers, chelators and lubricants that are necessary in the fabrication of plastics material.

In accordance with the present invention there is provided a radial block copolymer composition having a high degree of clarity and resealability and consisting essentially of (a) from 10%—90% by weight of a first butadiene-styrene radial block copolymer having a butadiene content of 85%—60% by weight and a styrene content of 15%—40% by weight, (b) from 90%—10% by 3418 - 4 weight of a second butadiene-styrene radial block copolymer having a differing butadiene-styrene content from said first copolymer and having a butadiene content of 85%—60% by weight and a styrene content of 15%—40% by weight and (c) from 5% to 75% by weight of the total weight of the radial block copolymer composition of a clear polymeric material which is an acrylic resin, a thermoplastic epoxide, a styrene-acrylonitrile copolymer, a polycarbonate, a polyester, a polyolefin, a polyvinyl— chloride, an olefin/vinyl chloride copolymer, a polyether or a polyester urethane polymer, a methacrylate-styrenebutadiene copolymer, a methyl methacrylate-acrylonitrilestyrene-butadiene copolymer or a mixture thereof. Of the foregoing those preferred are the thermoplastic polyether urethane polymers, the methyl methacrylatestyrene-butadiene copolymers, the methyl methacrylateacrylonitrile-styrene-butadiene copolymers and the thermoplastic polyester urethane polymers, and mixtures thereof.

In a preferred composition, the first radial block copolymer has a butadiene content of substantially 70% by weight ahd a styrene content of substantially 30% by weight and the second butadiene-styrene copolymer has a butadiene content of substantially 60% by weight and a styrene content of substantially 40% by weight with the copolymer having the 70:30 butadiene-styrene ratio present in an amount of from 90%—45% by weight and the polymer having the 60:40 butadiene-styrene ratio present in an amount of 10%—55% by weight with a 75% to 25% ratio most preferred.

In the following Examples, certain polymers, plasticizers, chelators, lubricants and antioxidants. - 5 are referred to in composing the novel compositions of this invention. All of the materials are readily available on the commercial market and a brief summary of them follows: Product Trade Name Source Polymers Radial block copolymer (70:30 butadiene-styrene) Radial block copolymer (60:40 butadiene-styrene) Solprene 411 Phillips Petroleum Co.

Solprene414 Phillips Petroleum Co.

Butadiene-styrene-methyl Acryloid methacrylate polymer KM—636 Thermoplastic polyether Roylar urethane E—85 Butadiene-styrene-methyl Acryloid methacrylate polymer KM—641 Rohm & Hass co.

Uniroyal Chemical Co., Division of Uniroyal, Inc. Rohm & Haas Co.

Butadiene -styrenemethacrylate-acrylonitrile polymer Blendex435 Marbon Division, Borg-Warner Corp.

Thermoplastic polyether Roylar urethane polymer E—80 Uniroyal chemical Co., Division of Uniroyal, Inc.

Thermoplastic polyester Estane urethane polymer 5701 Processing Aid B. F. Goodrich Chemical co.. Division of B.F. Goodrich Acrylic processing aid Acryloid K—175 Rohm & Haas Co.

Plasticizers Monomeric epoxy Mineral oil U.S.P. grade Epoxol Swift Chemical Co., 8—2B Division of Swift and Company — Any available Chelator Trisnonyl phenyl phosphite Mark 1178 Argus Chemical Co., Division of Witco Chemical Co. - 6 Product Trade Name Source Lubricants Mono fatty acid ester of fatty alcohols Loxiol G—40 Henkel, Inc. 5 Diglyceryl ester of unsaturated fatty acids Loxiol G—16 Henkel, Inc Complex ester of unsaturated fatty acids Loxiol G—71 & G—73 Henkel, Inc. 10 Antioxidaments Octadecyl 3-(3',5'-ditertbutyl -41-hydroxyphenyl) propionate Xrganox 1076 Ciba-Geigy 15 2,4-ditert.-p-butyl cresol Iono1CP Shell Chemical Tetrakis-|‘methylene-3(3·,5' di-t-butyl-4'- IrganoX 1010 Ciba-Geigy hydroxyphenyl) propionate] methane Of the above the words Solprene Blendex and Loxiol are Registered Trade Marks.

The invention is disclosed in further detail by means of the following Examples which are set forth for the purpose of illustrating the invention, but, in no way are to be construed as limiting the invention to the precise amounts, ingredients or conditions indicated.

Example I.

Formula by Ingredients Parts % Comp.

Radial block copolymer (70:30 butadiene-styrene) 75.0 58.73 Radial block copolymer (60:40 butadiene-styrene) 25.0 19.58 10 Butadiene-styrene-methyl methacrylate polymer (Acryloid KM—636) 10.0 7.83 Thermoplastic polyether urethane polymer (Roylar E—85) 10.0 7.83 15 Monomeric epoxy plasticizer 5.0 3.91 Chelator (tris nonyl phenyl phosphite) 0.5 0.39 Lubricant (mono fatty acid ester of fatty alcohols) 2.0 1.57 20 Antioxidant (octadecyl 3-(3'5' di-tert.-hutyl-4-hydroxypheny1)propiona te) 0.2 0.16 127.7 100.00 The indicated amounts of the ingredients are weighed out and placed in a low shear blender such as a Prodex-Henschel or a ribbon blender. The ingredients are mixed at a low speed for approximately five minutes to assure a good, dry blend. The resulting finished mixture can then be stored in suitable containers for future use in extrusion, injection molding or transfer molding. For tubing extrusion in a 2 or 2.5 inch 24/1 L/D extruder, the mixture is placed in a hopper and extruded using a single stage screw with heat 2ones between 300°—400°F. Tubing was extruded at a rate of 100 feet per minute and had an internal diameter of 0.100 inch and an outside diameter of 0.138 inch. The tubing was extruded in 3,000 foot lengths. For best - 8 4 3 4ΐθ transfer molding results, the mixture should be fused first into a slab form. The mixture can also be injection molded as a dry blend or in pelletized form.

Typical properties for the resulting material when fabricated as a female needle adapter with luer fittings at one end and tubing connector sleeve at the other end or as an I.V. bag reseal were as follows: Shore A 100% Ultimate Ultimate % Clarity Durometer Modulus Tensile Elongation +5 74 300 1875 697 Example II.

Formula by Ingredients Parts % Comp.

Radial block copolymer 75.0 (70:30 butadiene-styrene) Radial block copolymer 25.0 (60:40 butadiene-styrene) Butadiene-styrene-methyl 10.0 methacrylate polymer (Acryloid KM—641) Chelator (tris nonyl phenyl 0.5 phosphite) Lubricant (diglyceryl ester 1.0 of unsaturated fatty acids) Antioxidant (tetrakis- 0.2 [methylene-3-(3',5' di-tbutyl-4-hydroxyphenyl)propionate]methane) _ 111.7 67.10 22.40 9.00 0.40 0.90 0.17 100.00 The mixing and moulding procedures were the same as those used in Example I and a product when fabricated into tubing having the same internal and outside diameters as in that Example had the following properties Clarity - 9 - Ultimate % Elongation Shore A Durometer 100% Modulus Ultimate Tensile +3 75 358 3292 673 Example III. Ingredients Formula by Parts % Comp.

Radial block copolymer (70:30 butadiene-styrene) 75.0 65.96 Radial block copolymer (60:40 butadiene-styrene) 25.0 22.00 Butadiene-styrene-methacrylate-acrylonitrile polymer 10.0 8.79 Monomeric epoxy plasticizer 2.0 1.76 Chelator (tris nonyl phenyl phosphite) 0.5 0.44 Lubricant (mono fatty acid ester of fatty alcohols) 1.0 0.88 Antioxidant (2,4-ditert.-p- 0.2 0.17 butyl cresol) _ _ 113.7 100.00 The mixing and moulding procedures were the same as those used in Example I. The typical properties for product when fabricated into the same size of tubing in Example I were as follows: Shore A 100% Ultimate Ultimate % Clarity Durometer Modulus Tensile Elongation +3 400 3017 657 Example IV.

Ingredients Formula by Parts % Comp.

Radial block copolymer 75.0 (70:30 butadiene-styrene) Radial block copolymer 25.0 (60:40 butadiene-styrene) Thermoplastic polyether 10.0 urethane polymer (Roylar“ E—80) Monomeric epoxy plasticizer 2.0 Chelator (tris nonyl phenyl 0.5 phosphite) Lubricant (complex ester of 1.0 unsaturated fatty acids, Lioxiol G—7X) Antioxidant (2,4-ditert.-ρ- O.2 butyl cresol) _ 113.7 65.96 22.00 8.79 1.76 0.44 0.88 0.17 100.00 The mixing and molding procedures were the same as those used in Example I and the typical properties for a product when fabricated into the same size tubing as that of Example I and 13 and 20 mm. bottle closures were as follows: Shore A 100% Ultimate Ultimate % Clarity Durometer Modulus Tensile Elongation +4 350 3233 700 3 4 7 8 - 11 Example V Formula by Ingredients Parts % Comp.

Radial block copolymer (70:30 butadiene-styrene) 75.0 66.55 Radial block copolymer (60:40 butadiene-styrene) 25.0 22.18 Thermoplastic polyester urethane polymer 9.0 7.99 Monomeric epoxy plasticizer 2.0 1.77 Chelator (tris nonyl phenyl phosphite) 0.5 0.44 Lubricant (diglyceryl ester of unsaturated fatty acids) 1.0 0.89 Antioxidant (2,4-ditert.-pbutyl cresol) 0.2 0.18 112.7 100.00 The mixing and molding procedures were the same as those used in Example I and the typical properties for a product when fabricated into the same size of tubing and flexible Y reseal for I.V. sets were as follows: Shore A 100% Ultimate Ultimate % Clarity Durometer Modulus Tensile Elongation +4 78 367 3175 697 - 12 Example VI.

Ingredients Formula by Parts % Comp. Radial block coplymer (70:30 butadiene-styrene) 37.5 23.78 Radial block copolymer (60:40 butadiehe-styrene) 12.5 7.93 Butadiene-styrene-methyl methacrylate polymer (Acryloid KM—641) 100.0 63.40 Acrylic processing aid 3.0 1.90 Lubricant (complex esters of unsaturated fatty acids, Loxiol G—73) 2.0 1.27 Chelator (tris nonyl phenyl phosphite) ! 0.5 0.32 Antioxidant (2,4 ditert.-pbutyl cresol) 0.2 0.13 Plasticizer (mineral oil, U.S.P. grade) 2.0 1.27 157.7 100.00 The mixing and molding procedures were the same as those used in Example I and the typical properties for these ingredients when molded into a semirigid luer type needle adapter and sight chamber were as follows: Shore A 100% Ultimate Ultimate % Clarity Durometer Modulus Tensile Elongation +2 80 800 2300 450 Concerning the composition of Example VI, it should be pointed out that the clarity of this composition can be improved by using a different butadienestyrene-methyl methacrylate polymer or butadiene-styrene43418 - 13 methyl methacrylate -acrylonitrile polymer and eliminating the acrylic processing aid or making a lubricant substitution.

In the preceding Examples and following Table I, certain tests are referred to for the thermoplastic products produced in accordance with this invention.

They are described as follows: Clarity —ft grading using plasticized polyvinylchloride as a comparative control of +5.

The 100% Modulus, Ultimate Tensile and Ultimate % Elongation were obtained using ASTM test Method: D—412—66 using a Type C die and an Instron Tensile Tester (the word Instron is a Registered Trade Mark) (a) 100% Modulus is the force required to elongate the dumbbell-shaped sample 100% using a one-inch bench mark for reference. (b) Ultimate Tensile is the force per crosssectional area required to pull the sample apart. (c) % Elongation is the elongation of the sample at break. A one-inch bench mark is placed on the sample before elongation. Then the distance between the marks at break minus one inch multiplied by 100 gives the percent elongation.

Shore A Durometer is a procedure for determining indentation hardness of materials (ASTM—D—2240). The method is based on a specified indentor forced into the material under specified conditions.

In the foregoing Examples I and IV, a thermoplastic polyether urethane polymer was referred to.

These polymers are the linear reaction products of polyether glycols and aromatic diisocyanates. In addi43418 - 14 tion to being clear, they are especially suitable for forming reseal devices such as injection sites and pierceable stoppers because of their elastomeric properties. The urethane polymers of the thermoplastic polyester type utilized in Example V are the reaction products of linear hydroxyl terminated aliphatic polyesters, an aromatic diisocyanate and an aliphatic diol. Further, methyl methacrylate-styrene-butadiene copolymers are indicated for use with the blend of the radial block styrene-butadiene copolymers as well as the methyl methacrylate-acrylonitrile-styrene-butadiene copolymers. Other polymers or copolymers which can be utilized and still provide a degree of clarity with the basic blend of radial block copolymers are those which will impart unique properties such as hot strength and resistance to cold flow; will be compatible at working levels; can be used in nontoxic applications; will process at 300°—400°F. in the compound. These are the following polymers or copolymers; acrylic resins, thermoplastic epoxides, polycarbonates and polyolefins, polyesters, polyvinylchloride and olefin/vinyl chloride copolymers.

Certain components are utilized as being fabricated from the radial block copolymer composition of this invention. Others include various types of closures such as pharmaceutical closures, flexible containers, syringe plunger tips and elastomeric bulbs.

Certain amounts of the polymeric materials (c) relative to the combined weight of the radial block copolymers are indicated in the Examples. These amounts can be adjusted and still provide the advantages - 15 of this invention. For example, the methyl methacrylate-styrene-butadiene copolymers may be presai t in an amount of from 5 to 200 parts by weight per 100 parts by weight of the combined weight of the radial block copolymers; the polyether urethane in an amount of 10 to 50 parts by weight per 100 parts by weight of the combined weight of the radial block copolymers; the polyester urethane in an amount not exceeding 50 parts by weight per 100 parts by weight of the combined weight of the radial block copolymers; and the methyl methacrylate-acrylonitrile-butadiene-styrene in an amount of from 10 to 70 parts by weight per 100 parts by weight of the combined weight of the block copolymers.

Plasticizers may be incorporated into the foregoing compositions in varying concentrations in amounts of from 2 to 50 parts by weight per 100 parts by weight of the combined radial block copolymers. These plasticizers are those authorised for use by the U.S. Food and Drug Administration. The preferred plasticizers are U.S.P. grade mineral oil and monomeric epoxidized esters in concentrations of less than 10% by weight. Chelators, lubricants, antioxidants, pigments and fillers may be incorporated into these compositions in required concentrations. As indicated by the Examples, the compositions may be mixed or blended by conventional plastics or rubber mixing methods. For example, mixing may be done by simple tumbling, intensive mixers, open mill mixing, Banbury mixing or by extrusion and pelleting or dicing. The resulting product can be of various shapes and configurations such as plastic tubing or a drip chamber. 43418 - 16 The Table shows the properties obtained with twenty radial block copolymer compositions of differing butadiene-styrene content. Conclusions and applications which can be reached from this data are: 1. The Shore A durometer hardness increases with the higher styrene content. Higher durometer hardness are suitable for plastics molded parts, whereas lower durometer hardness are favored for closures. 2. Tensile strength increases with styrene content and preferred values exceed 25% by weight styrene content. 3. Ultimate elongation shows a desired maxima between 25 and 37% by weight, styrene content. 4. One-hundred percent modulus increases with styrene content. Values greater than 30% by weight styrene content, are desired for plastics usage in tubing and plastics molded parts. Values below 30% by weight of styrene, are desirable for closure applications .

. Alkaline extraction decreases with increased styrene content. It is desired to obtain the lowest values. 6. Optimum clarity is found between 25 and 35% by weight styrene content.

It should be pointed out that in all of twenty radial block copolymer formulations the additional polymers and additives employed in conjunction with the radial block copolymers are the same and are those illustrated in the previous Examples. It will also be 4341 - 17 10 seen from the Table that the preferred average molecular weight of the blend of the radial block copolymers is between 150,000 and 270,000.

It will thus be seen that the present invention 5 provides a novel plastics material composition which through its physical characteristics can be utilized for administering fluids to the body. The composition has a high degree of clarity yet can be processed by various plastic and rubber fabricating techniques.

Most importantly, the compositions have very low extrac tion values which makes them especially suitable for use in handling parenteral solutions. 43418 -18- οτ 77.4 KO CM CM r— * Γ- ΓΗ 266,1 26.6 272 I 1605 720 3358 +4 σ» | 33 67 27.7 200.5 27 250 οοττ 647 CM sp 56 +5 co | 48 | CM in Γ- Ο CM 22? ! 27.8 263 1338 667 30 1 55 : +5 I— •m* • r- r- 22.6 27.7 rH KO KD CM 29 co cn CM co 00 in 1- 740 KD CM sP KO rr + KD 1 75 25 L'LZ in CM KD CM 32.5 300 •ςρ CM | ; 713 CO O r- in + in 001 27.7 8 CM o Μ» [467 :3450 577 CO H 08 CM + o o rH 27.7 150 m rH o o rH 0 sp «—I 457 42 27 CH + CO 100 o o CM 150 25 225 693 O rH KD σ\ sP in sp +3 CM o o r-H 27.7 150 30 [ 250 673 527 47 in m sp + r—{ 100 Γ— ς Γ- ΓΗ o in o <3* CM CO r*- r-. Γ- ΙΟ *dL CM CM in KO co + o o • o ϋ ·* φ rH i—l q x . 2 * 4J «s·· 300 1 150 1 150 150 o in rH 250 Additional Polymers and Additives Ό CJ OJ rH ffl OH 0 4J £ ftf rH P 0 0 rH o ° 2 O O 0 & tn rH % Styrene in Blend 100S Modulus - psi Ultimate Tensile Strength - psi Ultimate Elongation - S Alkaline Extraction Nephelos Units M G) -P (1) £ 0 u 3 Q GJ M 0 Λ 01 Relative Clarity Styrene ?5 30 ! 40 1_ o ro in CM in rH o rt! ffl υ Q H Cm Radical Block Copolymer TABLE (Cont’d, [ 20161 tf GO 27.7 234 35.9 |373 1 [3007 [713 | 24 1 74 j +3 cn i—l 33 19 27.7 i 217 31.6 293 1633 |687 3951 1 +5 18 r4 k8 1 27.7 234 | 38417 3358710 1 1977 1 ra + i—l ra ra c- CD p- c· CJ 217 1 35 1352 ^847713 2970 1 •tf + CD τ—1 O tn os 1 Γ* c* CJ 200 1 32,5 I237 086 630 37 I OS in 4- 15 ra ra r* CD CJ 217 r* CD ra 425 3328 | 707 | 18 j 11 +3 t-l ! 1 O tn 1 os 1 c* CI 200 in ra 1333 1 CJ co r±650 ( CD CJ | 69 +4 ra r—l 25 j tn c· 27.7 150 32.5 283 | 707 j 517 | 40 58 [ in -P CJ r-l 1 33 19 1 P* r- CJ 200.5 120 1175 1532 1617 1 OS41 1 + r-l i—J 48 Cl in 27.7 222 [ 23.3 I217 sie| I537 cn in 149 +3 “O” o . o a * (U r-l «j s 300 | 150 o in rd o tn r—1 1 150 1 j 250 TJ β Wt. of Blend le Strength- psi %8 01 0 r-4 Φ A ft Φ β Ψ „ M £30 1 o sr 30 j tn CJ in i—l o 01 M tu 1 lend •rl 01 ft [ultimate Elongation - ction I meter £ ω ra υ Q H &) i—4 0 ft Ui fl r—1 β ra β •rl I ω β •rl 01 β Φ Alkaline Extra, Units Duroi [Relative Clari Radial Block Copolymer Additional Additives u 0 i—l tn ι-ί > |% Styrene Η β ϋ 0 S Η [ultimate 1 [Shore A 3418

Claims

1. CIA.IMS:1. A radial block copolymer composition having a high degree of clarity and resealability and consisting essentially of (a) from 10%—90% by weight of a first 5 butadiene-styrene radial block copolymer having a butadiene content of 85%—60% by weight and a styrene content of 15%—40% by weight, (b) from 90%—10% by weight of a second butadiene-styrene radial block copolymer having a differing butadiene-styrene content from said 10 copolymer and having a butadiene content of 85%—60% by weight and a styrene content of 15%—40% by weight and (c) from 5% to 75% by weight of the total weight of the radial block copolymer composition of a clear polymeric material which is an acrylic resin, a thermoplastic 15 epoxide, a styrene-acrylonitrile copolymer, a polycarbonate, a polyester, a polyolefin, a polyvinylchloride, an olefin/vinyl chloride copolymer, a polyether or a polyester urethane polymer, a methacrylate-styrene-butadiene copolymer, a methyl methacrylate-acrylonitrile-styrene20 butadiene copolymer or a mixture thereof.

2. A radial block copolymer mixture as defined in Claim 1 wherein said polymeric material (c) is a thermoplastic polyether urethane polymer, a methyl methacrylate-styrene-butadiene copolymer, a methyl methacrylate25 acrylonitrile-styrene-butadiene copolymer or a thermoplastic polyester urethane polymer, or a mixture thereof.

3. A radial block copolymer composition according to either Claims 1 or 2 wherein the amount of butadiene in said (a) portion of said radical block copolymer mixture is 30 substantially 70% by weight and said styrene amount is substantially 30% by weight and the amount of butadiene - 21 in said (b) portion of said radial block copolymer mixture is substantially 60% by weight and said styrene is substantially 40% by weight.

4. A radial block copolymer composition according to any of Claims 1 to 3 wherein said first radial block copolymer (a) is present in an amount of 90%—45% by weight and said second radial block copolymer is present in an amount of 10%—55% by weight.

5. A radial block copolymer composition according to any of Claims 1 to 4 wherein said first radial block copolymer (a) is present in an amount of 75% by weight and said second radial block copolymer (b) is present in an amount of 25% by weight.

6. A radial block copolymer composition as claimed in any preceding claim wherein component (c) is a methyl methacrylate-acrylonitrile-styrene-butadiene copolymer which is present in an amount of from 10 to 70 parts by weight per 100 parts by weight of the combined weight of said radial block copolymers (a) and (b).

7. A radial block copolymer composition according to any of Claims 1 to 5 wherein component (c) is a methyl methacrylate-styrene-butadiene copolymer which is present in an amount of from 5 to 200 parts by weight per 100 parts by weight of the combined weight of said radial block copolymers.

8. A radial block copolymer composition according to any of Claims 1 to 5 wherein component (c) is a thermoplastic polyether urethane polymer which is the linear reaction product of a polyether glycol and an aromatic diisocyanate. - 22 J34l 8

9. A radial block copolymer composition according to any of Claims 1 to 5 wherein component (c) is a thermoplastic polyether urethane which is present in an amount of 10 to 50 parts by weight per 100 parts by 5 weight of the combined weight of said radial block copolymers.

10. A radial block copolymer composition according to any of Claims 1 to 5 wherein component (c) is a thermoplastic polyester urethane and is' the reaction product 10 of a linear hydroxyl terminated aliphatic polyester, an aromatic diisocyanate and an aliphatic diol.

11. A radial block copolymer composition according to any of Claims 1 to 5 wherein said thermoplastic polyester urethane is present in an amount not exceeding 50 15 parts by weight per 100 parts by weight of the combined weight of said radial block copolymers.

12. A radial block copolymer composition according to any of the preceding claims which additionally includes a plasticizer composition in an amount of from 20 2 to 50 parts by weight per 100 parts by weight of the combined weight of said radial block copolymers.

13. A radial block copolymer composition as claimed in any of the preceding claims in which said plasticizer is mineral oil. 25

14. A radial block copolymer composition as claimed in any of the preceding claims in which the composition has been molded to form a medical plastic product

15. A medical plastic product according to claim 30 14 in the form of plastic tubing, a drip chamber, a - 23 reseal device, an adapter, a needle adapter, a closure, a syringe plunger tip, a flexible container and an elastomeric bulb.

16. The medical plastic product as defined in 5 Claim 15 wherein said closure is a pharmaceutical closure.